As a Passive House has an airtight and super insulated envelope, it means that there is a need for ventilation; hence a Mechanical Ventilation Heat Recovery unit is used.
A Mechanical Ventilation Heat Recovery unit or MVHR is used to take advantage of these conditions in a passive house; it brings fresh cold fresh air into the house, using the heat from the warm stale air exiting the house to heat up this fresh air.
The two air flows never meet so that the incoming fresh air is not contaminated with the outgoing stale air and only the heat is transferred.
Most units work on the basis of being around 80 – 90% efficient, so that most of the heat generated in the house is not wasted but recycled into the house. The other main benefit is the constant supply of fresh, filtered air within the building without the need to open windows.
